Process for treating iron-tanned leather.



UNITED STATES T OFFICE.

JOSEPH IBYSTRON, OF TESCHEN, AUSTRIA-HUNGARY, ASSIGNOR T0 HIMSELF, ANDKARL BARON VON VIETINGHOFF, OF BERLIN, GERMANY.

PROCESS FOR TREATING IRON-TANNED LEATHER.

No Drawing.

To all whom it may concern:

Be it known that I, JosnrnBrs'rnow, a citizen of the Empire ofAustria-I'Iungary, residing at Teschen, Bohemia, Austria- Hungary, haveinvented certain new and useful Improvements in Processes of TreatingIron-Tanned Leather, of which the fol lowing is a specification.

This invention relates to a process for treating leather tanned withiron salts with alkali salts, for instance, with common salt or sodiumsulfate. The resultof such a treatment is that more or less of the ironoxid contained in the leather is converted in the presence of iron saltsinto an insoluble basic salt of light color which in addition to theiron oxid also contains definite quantities of SO or Cl in a chemicallycombined state. The reaction takes place according to the followingequation:

The advantage of such a conversion is due to the favorable physicalproperties of the yellow insoluble basic ironsalt.

In contradistinctionto iron oxid which is a glass hard and similarlybrittle substance, the yellow insoluble iron salt is soft and mealy.

Leather which has only been tanned by means of iron oXid just as brittleand moreover just as liable to. crack as iron oxid itself. When,however, a suitable portion of the same is converted into the yellowinsoluble basic iron salt, the favorable physical properties of the samebecome effective and a soft and elastic leather is the result of'thetreatment. The eculiar action of the alkali salts on the iron tannedleather is due on the one hand to the nature of the salt itself. Sodiumsulfate for in stance possesses these properties to a great extent,whereas common salt is not quite so effective'in this respect, and thecorresponding potassium salts are even less so. Further the action, ofthe alkali salts also de- Specification of Letters Patent.

Patented May 13, 1 913.

Application filed September 26, 1912. Serial No. 722,472.

pends upon their quantity or concentration as that for instance, it ispossible to obtain with common salt just as strong an action as withsodium sulfate, provided that a pro portionately greater quantity of theformer is used.

A cha 'acteristic feature of the yellow insoluble iron salt is that itsformation re quires some considerable time. Generally several hours arenecessary for this purpose and the less there is of the particular saltthe longer will be the forn'lation process.

In carrying the process into effect, it is important that more or lessof the alkali salt be incorporated in the iron tanned leather. This maybe effected by fulling the leather with the concentrated salt solutionor by simply coating it with the same and allowing it to sink in. Theiron tanned leather may for instance be treated with a single or doublequantity of sodium sulfate of 10 degree Baum or with the same quantityof common salt of 25 I-laume, or the air dried leather is coated withsolutions of such salts. Generally speaking the amount to be useddepends upon the softness which it is desired to impart to the leatherand the most suitable mixing proportions must be determined for eachparticular case. After some time, that is, after the alkali salt hasexerted its action, it may bercmoved at the same time with the existingacid iron salts by washing the leather in water.

I claim:

The process herein described of treating leather tanned with iron salts,which consists in treating the leathcrwith neutral alkali metal saltsolutions.

In testimony that I claim the foregoing as my invention, I have signedmy name in presence of two subscribing witnesses.

JOSEPH BYSTRON. Witnesses:

ERNEST LILKS, MILLI BALLERS'IEINN.

